Field of the Disclosure
The present disclosure relates to an organic light emitting diode display device, and more particularly, to an active matrix type organic light emitting diode display device.
Discussion of the Related Art
Recently, with rapid development of information technologies, flat panel display (FPD) devices having thin profiles and light weight have been suggested and actively pursued. The flat panel display devices are represented by a liquid crystal display devices and an organic light emitting diode display devices. Since the organic light emitting diode display devices do not need additional light sources such as backlights of the liquid crystal display devices but display sharper images than the liquid crystal display devices.
An organic light emitting diode display devices include pixels which are arranged in a screen, each of which may be comprised of sub-pixels of different colors. The sub-pixels are defined by crossing of gate lines and data lines. Each sub-pixel may be independently driven by driving elements including thin film transistors; the thin film transistors and metallic lines may be disposed in a driving element region. At this time, if the thin film transistors and the metallic lines in the driving element region reflect outside light, outer visibility may be lowered.
FIG. 1 is a cross-sectional view of illustrating a part of an active matrix type organic light emitting diode display device according to the related art.
In FIG. 1, the organic light emitting diode display device of the related art includes an organic light emitting diode 120 and a polarizer 110 formed on a substrate (not shown) through which light emitted from the organic light emitting diode 120 is transmitted to the outside.
The organic light emitting diode 120 includes an anode electrode 121, an organic light-emitting layer 122 and a cathode electrode 123.
When holes injected from the anode electrode 121 are combined with electrons from the cathode electrode 123, exitons are formed. At this time, light is emitted with a band gap energy of the organic light-emitting layer 122. The emitted light passes a color refiner 130 and is converted to a desired color.
The polarizer 110 includes a linear polarizer 111 polarizing incident light and a λ/4 phase retarder 113. The linear polarizer 111 and the λ/4 phase retarder 113 are held together in between by a first adhesive layer 112.
Light from outside is linearly polarized through the linear polarizer 111, which may be a horizontal linear polarizer. Thus, light from the outside is horizontally polarized (linear). Furthermore, the linearly polarized light is circularly polarized through the λ/4 phase retarder 113. For example, it may be left-circularly polarized. The circularly polarized light is reflected by the cathode electrode 123 and passes through the λ/4 phase retarder 113 again. When reflected, the left-circularly polarized light is right-circularly polarized. And through the λ/4 phase retarder 113 it is vertically polarized (linear). Since the vertically polarized (linear) light cannot pass through the horizontal linear polarizer 111, light from the outside cannot be reflected and the visibility can be improved.
A second adhesive layer 114 is formed outside of the λ/4 phase retarder 113 and adheres the polarizer 110 to the organic light emitting diode display device.
When the reflection of outside light is minimized using the polarizer 110, less than 45% of light emitted from the organic light emitting diode 120 is transmitted, and more than half of the brightness is deceased. Therefore, if more power consumption is used to compensate the deceased brightness, the lifetime of an organic light emitting layer 122 is reduced.
Further, since the polarizer 110 is relatively expensive, adopting polarizer 110 in order to block the reflection is not so competitive.